These ERS-2 orbits are based on SLR and fast-delivery altimeter crossovers and
normal points. The orbit files
were made available with a latency of about a week. They were updated on Tuesday and Friday
afternoon and mirrored on both FTP sites.

New EIGEN-GRACE01S and EIGEN-CG03C orbits for ERS-2 and Envisat ...

These ERS-2 orbits are currently based on SLR data only, after the failure of
the last on-board tape recorder and the end of the global ERS-2
altimetry dataset in June 2003. Enhanced gravitational and non-gravitational force
models are used to maintain the best attainable orbit accuracy. Orbits
with these models have been back-processed to cycle 70, corresponding
to December 2001/January 2002. The orbit files are available with a
latency of 1 to 3 months.

These Envisat orbits are based on SLR and DORIS data.
The orbit files are available with a latency of 1 to 3 months,
depending on the availability of DORIS tracking data.

Note that the EIGEN-GRACE01S orbits for Envisat processed after the summer of 2006 contained a bug in the processing, causing them to be slightly less accurate (< 2 cm RMS error), and systematically too high by about 5 mm, from cycle 30 onwards. All users of these Envisat orbits, especially altimetry users, are recommended to replace all their EIGEN-GRACE01S orbits with the new EIGEN-CG03C orbits.